Aquifer Material Research Articles

Application of electrical resistivity tomography for groundwater evaluation in Yirgacheffe Town and its environs, Main Ethiopian Rift

Exploring groundwater is crucial in areas with poor surface water quality, such as Yirgacheffe Town and its surroundings. This study aims to assess aquifer materials and groundwater potential using Electrical Resistivity Tomography (ERT) in the region,within the Main Ethiopian Rift. Four electrical resistivity profiles were gathered using a Wenner array with a WDA-1 digital resistivity and induced polarization meter from Chongqing, China. Each profile extended 236 m with 4-m electrode spacing. Data were analyzed and inverted with Res2DinV software and validated against lithological logs. The ERT inversion revealed three subsurface geoelectric layers: (1) massive rhyolite ignimbrite and basalt (>2000 Ωm); (2) weathered rhyolite ignimbrite and basalt (200–2000 Ωm); and (3) topsoil (4–200 Ωm). These results are key for effective water resource management and highlight ERT's utility in similar geological settings.

Geochemistry of fluoride mobilization in the hard-rock aquifers of central India: Implication for fluoride-safe drinking water supply

Globally, groundwater contamination by fluoride (F−) is a threat to the safe drinking water supply. Nevertheless, our understanding of the geochemical processes of F− mobilization to the groundwater by linking groundwater and aquifer material chemistry is limited. We therefore characterized that in the hard-rock aquifers of Central India, an area that has not been investigated thoroughly despite the known severity of the problem. Exploratory drilling of boreholes (n = 45) and lithostratigraphic modeling identified weathered basalt, vesicular basalt, fractured basalt, sandstone of Lameta, and fractured granite as major aquifers in the study area. The groundwater contamination by F− (concentration >1.5 mg/L) mainly occurred at depths >35 m bgl (at elevations <500 m amsl) of the fractured basalt and fractured granite aquifers, while samples collected from the shallow basalt, sandstone of Lameta, and shallow granite were mostly safe. The F− contamination of groundwater was primarily governed by the chemical evolution of groundwater along the flow path. Solute mass balance in groundwater, in conjunction with the mineralogical characterization of the aquifer materials, suggests that weathering of silicate and carbonate minerals was the dominant form of mineral dissolution in aquifers, which consumed dissolved CO2 along the flow path and resulted in an alkaline pH (>8) in groundwater of the deeper aquifers. The mobilization of F− in the groundwater could primarily be attributed to the ion exchange between OH− in water and structural F− in fluorapatite and F-bearing mica/amphibole. By assessing water quality and aquifer properties, this study suggests that primarily, the sandstone of Lameta and weathered and vesicular basalts can be targeted for F-safe drinking water supply in the study area. Targeting shallow aquifers can be an option for F-safe drinking water supply in other affected areas with similar geological and environmental settings.

Identification of Aerobic ETBE‐Degrading Microorganisms in Groundwater Using Stable Isotope Probing

AbstractA limited number of microorganisms have been identified with the capability to degrade ethyl tert‐butyl ether (ETBE) in the environment. Knowledge of the identity and distribution of ETBE‐degrading microorganisms is important for the implementation of management measures such as natural attenuation and bioremediation at ETBE‐release sites. In this study, DNA‐stable isotope probing (SIP) was used to identify microorganisms able to aerobically degrade 13C‐labeled ETBE in laboratory microcosms constructed with groundwater and aquifer material from an ETBE‐release site. Microorganisms in the Class γ‐proteobacteria, Order β‐proteobacteriales, Family Burkholderiaceae, and classified as Methylibium and Leptothrix, respectively, were identified as primary ETBE degraders. Comparisons with ETBE‐responsive microorganisms (those which increased in abundance after the addition of ETBE), identified by high‐throughput sequencing of microcosms established from the same site, showed that only a small proportion of the ETBE‐responsive organisms were primary degraders as determined by SIP. ETBE degraders were taxonomically related to microorganisms able to degrade other gasoline components, but not ETBE, implying that this functionality results from acquisition of the eth gene cluster by these organisms. These ETBE degraders could also be identified at ETBE‐release sites, but at low relative abundance and generally only in those locations from which the microcosms had been established. Therefore, we recommend that molecular investigations of ETBE‐contaminated sites focus on functional genes (i.e., the eth gene cluster) rather than specific taxa.

Groundwater Characteristics’ Assessment for Productivity Planning in Al-Madinah Al-Munawarah Province, KSA

In recent times, drilling groundwater wells for irrigation, domestic, and industrial uses is increasing at a high rate in Saudi Arabia, meaning that groundwater is becoming a primary water resource. In the study region, over-exploitation and unsustainable performance severely deteriorate groundwater. Therefore, it is important to monitor the groundwater levels and quality as well as to detect the hydraulic parameters in order to plan and maintain groundwater sustainability. Knowledge of aquifer hydraulic parameters and groundwater quality is essential for the productivity planning of an aquifer. Therefore, this study carried out a thorough analysis on measured depth to groundwater data (2017 and 2022), borehole pumping test records, and chemical analysis of the collected water samples, especially in the presence of overexploitation and scarcity of recharge scale. To accomplish this aim, measurements of 113 groundwater wells (including 103 water samples) and analysis of 29 pumping tests between step and long-duration tests were made of all aquifer characteristics. These parameters consist of well loss, formation loss, well efficiency, specific capacity, transmissivity, hydraulic conductivity, resulted drawdown, and physiochemical parameters. Thematic maps were generated for all parameters using the geographic information system (GIS) and diagrams to strategize the groundwater productivity in Al-Madinah Al-Munawarah Province. The estimated hydraulic parameters are highly variable. Four distinct portions were identified for aquifer potentiality based on these varying ranges. Both the north and east of the region are good for groundwater productivity due to good aquifer materials, whereas the southwestern and western portions have relatively poor values. The analyzed groundwater was categorized as fresh to slightly salty water, with two primary chemical types identified showing a prevalence of mixed NaCl and Ca-Mg-SO4/Cl water. Finally, groundwater productivity assessment predicts that the aquifers can support the Al-Madinah Al-Munawarah Province demand for several years if certain well distributions are adopted and for a few hours/day of pumping rate. The maps that have been created can be examined to aid in making decisions related to hydrology.

Geoelectric Investigation for Groundwater in Imo State University Campus and Environs using Direct Current Electrical Resistivity Method

Eighteen, vertical electrical soundings (VES), were carried out in Imo State University and Environs to delineate the potential site for groundwater. Data were acquired using ABEM SAS 300 resistivity meter. Schlumberger array and maximum electrode spread of 700m were adopted. Data were interpreted with IP2WIN software. Contour maps were done using Sulfer 20 software. Geoelectric cross-sections constructed along three profile lines delineated subsurface stratification. Sediments consist of sequence of sandstone/gravel, silty sand/sand and clay with geology representing the Benin Formation. Groundwater was delineated within the zone interpreted to be sand with quartz making up more than 95% of all grains. Resistivity of aquifer varies across study area and ranges from 159Ωm, observed around Library and Information Department (VES 11) to 100000Ωm recorded at IMSU Plaza (VES 10). Depth to water table also varied across study area with higher values of 150m and 130m observed at College of Health Science (VES 3) and Behind Old ETF (VES 4). A relatively shallow aquifer is delineated behind Senate Building and Okwu-Uratta with water table at depths of 23.5m and 26.5m. The transmissivity values are moderately high except at some locations. The variation in longitudinal conductance and transverse resistance values show that part of the study area such as Aso Rock, Female Hostel, Law Faculty and IMSU Plaza are underlain by relatively resistive (low longitudinal conductance) aquifer material. Distribution of hydraulic conductivity and electrical conductivity values indicates that in some of the VES points, the values are fairly constant. This could be seen as areas with similar geologic settings and water quality. Storativity of study area ranges from 0.00003 at VES 1 and 12 to 0.00028 at VES 4. Study area shows a good prospect for groundwater development, except at Library and Information Department, where the zone delineated is an aquitard.

Combined effects of geological heterogeneity and discharge events on groundwater and surface water mixing

Stream water (SW) infiltration to the subsurface and subsequent mixing with groundwater (GW) is crucial for controlling water quality in river-corridors. Mixing of solutes from SW and GW triggers biogeochemical reactions, which can attenuate contaminant influx from upstream SW or from GW that eventually enters the river in downstream regions. It is known that geological heterogeneity affects SW-GW exchange fluxes (EF), however, the combined effects of both hydrological and geological aspects (e.g., sand fraction present in the aquifer material) on EF and on SW-GW mixing in strong contrasting bimodal aquifer units remain unclear. Here, we examined this gap by combining geostatistical realizations, fully-integrated numerical flow simulations, and a mixing-cell routine to assess the major controls on EF and to evaluate how mixing develops and is affected by stream discharge events with different magnitudes and durations. Results show that subsurface heterogeneity at the river-reach scale mainly affects EF magnitudes rather than EF patterns. Yet, both EF magnitudes and SW-GW mixing increased with the introduction of subsurface heterogeneity and with the increase of average hydraulic conductivity (K) values and sand fraction in the models. The simulations further indicated a larger potential for mixing under more frequent, short events regardless of the aquifer material, however, mixing values were generally higher for sandier and heterogeneous models. Lastly, for a high K contrast between subsurface units, these effects were more pronounced. This characterization is critical for river restoration strategies and for downstream management of dam-regulated rivers. Our study elucidates the interplay between hydrological and geological controls on the development of SW-GW mixing at intermediate scales and highlights the importance of considering aquifer characteristics in future studies.

Extended Aquifer System Pressure Behavior under Carbon Storage

Summary Most reported carbon storage projects have involved inexpensive carbon dioxide (CO2) capture from gas processing plants or ethanol refineries. However, widespread carbon capture and storage (CCS) application must avoid any risk that high capital investment cost for carbon capture from stationary point sources leads to unanticipated issues related to the aquifer storage. This paper reviews successful and unsuccessful carbon storage projects and explains simple extended aquifer system fundamentals that must be considered in selecting a storage aquifer. This study begins by evaluating reported carbon storage projects in the context of an extended aquifer system with specific attention to initial formation pore pressure and potential or known hydraulic vertical or lateral communication with hydrocarbon accumulations and/or fresh water. Further study focuses on how the contrast between injection well and aquifer pressure evolution enables understanding of the overall aquifer material balance. Finally, we consider implications of brine migration during and after long-term CO2 injection in unconfined aquifers. Experience in the petroleum industry with aquifer behavior includes presence or lack of water influx and production from hydrocarbon reservoirs that share a common aquifer. Of particular importance is the observation that hydrostatic initial formation pressure indicates the possibility that a petroleum system, or an extended aquifer system without hydrocarbon accumulation(s), connects to atmospheric pressure through an unconfined aquifer. In such cases, indefinite injection will never increase the regional aquifer pressure. Furthermore, initial formation pressure that exceeds hydrostatic pressure implies a petroleum system or an extended aquifer system that is volumetrically limited. In such cases, injection will increase the system pressure, and pressure monitoring can detect leakage from the system. Finally, CO2 injection into an aquifer will displace brine in the direction of lower pressure that could relate to distant production from the same aquifer or from hydrocarbon reservoirs with which it communicates. Reasons for known carbon storage project interruptions have included unexpected lateral plume migration or aquifer pressure increase during CO2 injection that might have been anticipated with attention to straightforward consideration of aquifer-enabled hydraulic communication. Such extended aquifer dynamics must be included in long-term models for permanent CO2 storage during and after injection.

Hydrogeochemical characteristics and air quality risks associated with gold mining operations in Egypt using geochemical modeling and risk indices

The success of industrial operations depends on the effective identification, appraisal, and mitigation of possible hazards and associated environmental concerns. This report provides a complete review of environmental management techniques at the Sukari Gold Mine (SGM), located in the southeastern desert of Egypt. Extensive environmental measurements were taken to assess air and water quality, identify hazards, and analyze risks on the SGM premises. Air quality and noise intensity levels were measured at 39 places around the mine's working region. The findings found noncompliance with the Egyptian Environmental Law's (EEL4/94) noise exposure limitations, with the Power Generator House having the maximum noise levels at 107 dB. Remedial measures such as personal protective equipment (PPE) and exposure limit reduction strategies are being considered to address elevated noise levels. Measurements of particulate matter (PM10) and noxious gases (e.g., CO, SO2, NO2, HCN, and NH3) were conducted in workplace and ambient environments. Elevated PM10 concentrations were particularly concerning in underground regions, forcing the deployment of water depression techniques and improved PPE measures. While gas emissions from most activities remained under regulatory limits, select zones showed hydrogen cyanide (HCN) levels that exceeded permitted thresholds, necessitating specific control actions. Using hazard index (HI) and risk rating assessments, this study found different risk profiles across SGM's workplaces, focusing on high-risk regions for focused intervention. Additionally, a water assessment near a Tailing Storage Facility (TSF) was conducted to monitor the impact of mining activities on groundwater quality. The study revealed that groundwater in the region belongs to the Na–K–Cl–SO4 and Ca–Mg–Cl–SO4 water classes, with potential degradation attributed to high mineralization processes induced by aquifer materials and seawater intrusion. The findings underscore the importance of ongoing monitoring, control measures, and implementation of programs to ensure environmental sustainability and minimize risks associated with mining activities in the Sukari Gold Mines. This research highlights the imperative of continuous monitoring, proactive control measures, and the implementation of environmental initiatives to ensure the sustainability of mining operations within the Sukari Gold Mines.

Cr(VI) Reduction and Sequestration by FeS Nanoparticles Formed in situ as Aquifer Material Coating to Create a Regenerable Reactive Zone.

Remediation of large and dilute plumes of groundwater contaminated by oxidized pollutants such as chromate is a common and difficult challenge. Herein, we show that in situ formation of FeS nanoparticles (using dissolved Fe(II), S(-II), and natural organic matter as a nucleating template) results in uniform coating of aquifer material to create a regenerable reactive zone that mitigates Cr(VI) migration. Flow-through columns packed with quartz sand are amended first with an Fe2+ solution and then with a HS- solution to form a nano-FeS coating on the sand, which does not hinder permeability. This nano-FeS coating effectively reduces and immobilizes Cr(VI), forming Fe(III)-Cr(III) coprecipitates with negligible detachment from the sand grains. Preconditioning the sand with humic or fulvic acid (used as model natural organic matter (NOM)) further enhances Cr(VI) sequestration, as NOM provides additional binding sites of Fe2+ and mediates both nucleation and growth of FeS nanoparticles, as verified with spectroscopic and microscopic evidence. Reactivity can be easily replenished by repeating the procedures used to form the reactive coating. These findings demonstrate that such enhancement of attenuation capacity can be an effective option to mitigate Cr(VI) plume migration and exposure, particularly when tackling contaminant rebound post source remediation.

Source of arsenic pollution in southern Indus alluvial plain aquifers, Pakistan

Aquifers in Indus alluvial plain are naturally polluted by arsenic (As). Millions of population in Pakistan use groundwater for drinking is exposed to As ingested diseases. Present investigations were focused on the mobilization mechanism of As in the alluvial aquifers, in Matiari district of Pakistan, which is mainly covered by alluvial sediments of Holocene and Pleistocene age. These sediments are weathered from Himalayas and its neighboring regions and are primarily deposited by Indus River. About 94 samples of groundwater were collected from various localities of Matiari district. Physico-chemical data revealed that 60% of wells exceed 10 μg/L, WHO permissible standard for drinking water. Low nitrate and neutral to near neutral pH and negative Eh in most of the wells are indicative of reducing conditions in the aquifers. Ancient courses of Indus river and domestic and agricultural wastes could be an important source of organic matter. Microbiodegradation of organic matter has created reducing conditions in the aquifer, which trigger the reduction of sedimentary iron oxyhydroxides and the mobilize As in shallow aquifers of Matiari. A borehole was also drilled to decipher the lithological and geochemical characteristics of aquifer material. Elemental, petrographic and SEM-EDS data revealed that sediments are comprised of brown aquitard clay and well sorted grey fine sand. Arsenic in sand and clay samples ranged between 0.8 and 3.9 mg/kg and 0.3–3.2 mg/kg respectively. Dominant minerals in the aquifers sediments are phlogopite and biotite. Leaching of these minerals under reducing conditions is likely to provide higher concentration of As in the groundwater of the area.

Method validation of an inductive measurement system (IMS) for nanoscale zero-valent iron (nZVI) particles determination in sand-packed columns

The purpose of this work was to develop and validate a rapid, non-destructive, real-time measurement system for nanoscale zero-valent iron (nZVI) particles determination in sand-packed columns. This aims to provide an approach to analyse for nZVI particle transport and nZVI induced contaminant degradation reactions in 1-dimensional aquifer experiments. The inductive measurement system (IMS) was developed and tested by measuring columns filled with varying portions of nZVI and sandy aquifer material. Method validation was conducted for this innovative approach in accordance with several guidelines in disciplinary areas. The linearity of ZVI concentration and measurement signal was confirmed. Calibration curves were determined to be linear over the range of 0.11–53.50 g/L for nZVI NANOFER STAR, 0.10–81.67 g/L for nZVI BASF 1, 0.12–58.26 g/L for nZVI Carbo-Iron, 0.12–69.70 g/L for nZVI NANOFER 25DS ORM, 0.12–50.69 g/L for nZVI NANOFER 25DS, and 0.21–1613.39 g/L for nZVI Höganäs 1* (dry). This method was determined to be sensitive in nZVI, accurate (101.63 % within-run recovery, 101.85 % between-run recovery covering 76 days), and precise (0.46 % repeatability RSD, 0.85 % intermediate precision RSD covering 76 days). LOQ was determined ranging from 0.10 to 0.21 g/L for nZVI used in experiments and regression through origins was selected as the calibration model. Quality control processes were performed to assure the reliability of the results and the long-term stability. Additional data processing steps allowed to compensate for measurement deviations resulting from different liquid phase compositions, e.g. dispersants used for nZVI suspensions. This method is now successfully validated in single-laboratory conditions.

Mobility of Rare Earth Elements in Coastal Aquifer Materials under Fresh and Brackish Water Conditions.

The indispensable role of rare earth elements (REEs) in manufacturing high-tech products and developing various technologies has resulted in a surge in REE extraction and processing. The latter, in turn, intensifies the release of anthropogenic REEs into the environment, particularly in the groundwater system. REE contamination in coastal aquifer systems, which serve as drinking and domestic water sources for large populations, demands a thorough understanding of the mechanisms that govern REE transport and retention in these environments. In this study, we conducted batch and column experiments using five representative coastal aquifer materials and an acid-wash sand sample as a benchmark. These experiments were conducted by adding humic acid (HA) to the REE solution under fresh and brackish water conditions using NaCl, representing different groundwater compositions in coastal aquifers. The REEs were shown to be most mobile in the acid-wash sand and natural sand samples, followed by two types of low-carbonate calcareous sandstone and one type of high-calcareous sandstone and the least mobile in red loamy sand. The mobility of REEs, found in solution primarily as REE-HA complexes, was controlled mainly by the retention of HA, which increases with increasing ionic strength and surface area of the aquifer material. Furthermore, it was found that the presence of carbonate and clay minerals reduces the REE mobility due to enhanced surface interactions. The higher recoveries of middle-REE (MREE) in the column experiment effluents observed for the acid-wash sand and natural sand samples were due to the higher stabilization of MREE-HA complexes compared to light-REE (LREE) and heavy-REE (HREE) HA complexes. Higher HREE recoveries were observed for the calcareous sandstones due to the preferred complexation of HREE with carbonate ions and for the red loamy sand due to the preferred retention of LREE and MREE by clay, iron, and manganese minerals.

Organic matters, but inorganic matters too: column examination of elevated mercury sorption on low organic matter aquifer material using concentrations and stable isotope ratios

Abstract. Sorption of mercury (Hg) in soils is suggested to be predominantly associated with organic matter (OM). However, there is a growing collection of research that suggests that clay minerals and Fe/Mn oxides are also important solid phases for the sorption of soluble Hg in soil–groundwater systems. We use a series of (60 mL syringe based) column experiments to examine sorption and subsequent desorption of HgCl2 solutions (experiment 1 (EXP1): 46.1 ± 1.1 mg L−1; experiment 2 (EXP2): 144 ± 6 mg L−1) in low-OM (0.16 ± 0.02 %) solid-phase aquifer materials. Analyses of total Hg concentrations, Hg speciation (i.e. pyrolytic thermal desorption (PTD)), and Hg stable isotopes are performed on both solid- and liquid-phase samples across sorption and desorption phases of the experiments. The sorption breakthrough curve best fitted a Freundlich model. Despite the very low-OM content, the Hg equilibrium sorptive capacity in these columns is very high: 1510 ± 100 and 2320 ± 60 mg kg−1 for EXP1 and EXP2, respectively, and it is similar to those determined for high-OM soils. Data from the experiments on mass-dependent Hg stable isotope fractionation data from these experiments (described by δ202Hg) support preferential sorption of lighter isotopes to the solid-phase materials with results indicating an isotopically heavier liquid phase and an isotopically lighter solid phase. Desorption fits exponential decay models, and 46 ± 6 % and 58 ± 10 % of the sorbed Hg is removed from the solid-phase materials at the termination of desorption in EXP1 and EXP2, respectively. The divergence of δ202Hg values between liquid and solid phases also continues into desorption. This desorption profile is linked to the initial release of easily exchangeable Hg(II) species physically sorbed to Fe/Mn oxides and clay mineral surfaces (liquid phase enriched in heavy isotopes) and then slower release of Hg(II) species that have undergone secondary reaction to more stable/less-soluble Hg(II) species and/or diffusion/transport into the mineral matrices (processes favouring lighter isotopes; solid phase enriched in lighter isotopes). The secondary production of Hg(0) within the columns is confirmed by PTD analyses that indicate distinct Hg(0) release peaks in solid-phase samples at &lt;175 ∘C, which again agrees with field observations. Retardation (RD) and distribution (KD) coefficients are 77.9 ± 5.5 and 26.1 ± 3.0 mL g−1 in EXP1, respectively, and 38.4 ± 2.7 and 12.4 ± 0.6 mL g−1 in EXP2, respectively. These values are similar to values derived from column experiments on high-OM soil and provide the basis for future Hg fate and transport modelling in soil–groundwater systems.

Migration behavior of fugitive methane in porous media: Multi-phase numerical modelling of bench-scale gas injection experiments

Two-dimensional multi-phase numerical simulations based on detailed laboratory experiments are used to provide insight into the key processes of methane migration in porous media and to analyze the suitability of a continuum approach for modelling gas migration at the intermediate bench-scale. The simulations were conducted using the multi-phase numerical model DuMux, including groundwater flow, transport of free-phase methane subject to capillary and buoyancy forces, kinetic-controlled dissolution of methane into the flowing groundwater, and advective-diffusive transport of dissolved-phase methane. Mass transfer kinetics are controlled by the water-gas interfacial area, avoiding the assumption of thermodynamic equilibrium which was shown not applicable under these conditions of high aqueous velocity in sandy materials.The model is applied to a series of 2D laboratory experiments in which gas-phase methane was injected near the bottom of a 1.5 m square vertical flow cell under a background flow gradient and with homogeneous and heterogeneous configurations. Simulations are compared to the observed behavior with respect to gas-phase mass distribution over time, gas-phase saturations, and to breakthrough of the dissolved-phase methane at selected monitoring points. In this first comparative study (simulations vs real data), insights are provided into the role of spatial property distributions on methane migration, in particular gas-phase pooling below low-permeability layers. Similar to the laboratory results, the simulations confirmed that the concentrations of dissolved-phase methane are strongly dependent on the structure of the gas-phase plume which in turn is influenced by the geology. We show that at the local metre-scale, kinetic-controlled mass transfer is needed to reproduce the dissolved-phase methane concentrations. Nevertheless, an assessment of capillary parameter values typically encountered in sandy aquifer materials suggests that an equilibrium approach could still be suitable for field-scale simulations.

New Insights into the Formation and Properties of Wellbore Skin: Why We Have to Rethink the Concept.

The deposition of fine-grained material of low permeability on the borehole wall during drilling (wellbore skin) is a common problem affecting the operation and efficiency of water wells. Here, we present new data and novel insights from four excavated dewatering wells from a lignite surface mine. All wells have the same age, are of similar construction, and were sampled at two different depths each. The thickness of the skin layer increases with depth. Its composition and permeability is strongly influenced by the surrounding aquifer material. Nonuniform sediments of low permeability result in less permeable wellbore skin deposits. The presence of discontinuities in the skin layer may be a determining feature for the resulting flow to wells, especially with skin layers of low permeability. The presence of naturally occurring swelling clay (smectite) provides the skin layer with a significant self-sealing capacity.

Impact of Type and Shape of Microplastics onthe Transport in Column Experiments.

The pervasive nature of plastic and the longevity of plastics leaves a legacy of microplastics (MPs) that contaminate our environment, including drinking water sources. Although MPs have been documented in every environmental setting, a paucity of research has focused on the transport and fate of MPs in groundwater. Previous field and laboratory studies have shown that MPs can migrate through aquifer material and are influenced by environmental factors. This study used controlled column experiments to investigate the influence of polymer type (polyamide, polyethylene, polypropylene, and polyester) and particle shape (fragment, fiber, and sphere) on MP retardation and retention. The results showed that all individual MP types investigated were retarded compared to the NaCl tracer, with a retardation factor ranging from 1.53 to 1.75. While hypothesized that presence of multiple types and shapes could change mobility, the results indicate that this hypothesis is not correct for the conditions tested. This study provides new insights into MP transport in groundwater systems based on the characteristics of MP particles. In addition, this study demonstrates the need for further research on types of MPs and under more conditions, especially in the presence of a mixture of types and shapes of MPs to gauge what is occurring in natural systems where many MPs are present together.

Predicting Earth-Vas2 parameters of coastal plain sand aquifers using artificial neural Network(s), in the Calabar region of Nigeria

This study employs artificial neural networks (ANNs), specifically the Nonlinear Autoregressive with External Input (NARX) model as an ANN add-on for Matlab, to forecast Earth-Vas2 parameters. The model leverages a time series approach, with the Earth-Vas2 index (y(t)) as the predictive target and various parameters (elevations, static water level, aquifer material thickness, transmissivity, hydraulic conductivity, specific capacity, vadose media) denoted as x(t) to facilitate accurate predictions. The Levenberg-Marquardt training algorithm was applied to the ANN using geo-hydraulic data from 56 boreholes for training and 24 boreholes for validation and testing. Validation metrics such as mean square error (MSE), correlation coefficient (R), and coefficient of determination (R2) were utilized. The results indicate a high degree of accuracy, with low MSE values of 0.0171 (training), 0.0087 (validation), and 0.0327 (testing). Strong correlation coefficients (R) of 0.9882, 0.9898, and 0.9844, along with high R2 values (97.66%), emphasize the robustness of the ANN model. Actual and predicted Earth-Vas2 values exhibit a similar pattern, affirming the model's effectiveness. The R-value of 0.9882 signifies a strong positive correlation within the model, validating its ability to capture variable interactions in fluid migration control. Geo-hydraulic Earth-Vas2 maps identify areas with varying migration efficiency, guiding groundwater management. The study emphasizes routine subsurface assessments for crucial data in environmental planning and risk reduction in industrial and municipal activities. This method provides cost-effective estimation of key geo-hydraulic properties for aquifer vulnerability assessments, with far-reaching implications for groundwater management, environmental protection, and land use planning.

Exploration of Ground Water Potential of Federal University of Technology, Owerri and Its Environs Using Resistivity Survey

The research focused on evaluating the groundwater potential in the vicinity of Federal University of Technology Owerri (FUTO) using a resistivity survey method. The investigation involved the utilization of eleven Schlumberger vertical electrical soundings (VES). The data collection was conducted using an ABEM Terrameter SAS4000 and then processed with IPI2Win Software, which relies on the conventional theory of curve matching. This process aimed to determine the depth, quality, and subsurface formations of the groundwater. The VES interpretation results revealed the presence of 3-5 geoelectric layers above the aquiferous layers. Various curve types were identified in the study area, including monotonically ascending (AA), bowed-ascending (HA), bowl-bell (HK), and ascending-bell (AK) curves. The majority of the field curves were found to be of the A-shaped type, signifying specific aquifer characteristics. The study indicated that the depth to the water table is relatively shallow in the Ihiagwa area, with an average depth of 7.26 meters. In contrast, the aquifer's depth is deeper around Avu, Nekede, and Eziobodo areas, with a mean depth of 32.33 meters. Obinze had very deep aquifers, with an average depth of 57.75 meters. Furthermore, the study established a relationship between aquifer characteristics and geoelectric parameters, allowing for the estimation of hydraulic conductivity and transmissivity values at all the sounding locations, even in areas lacking boreholes. These hydraulic characteristics showed that the aquifer had protective capacities ranging from 0.036 to 0.509 mhos, transmissivity values ranging from 11856.32 to 28661.28 m2/day, and hydraulic conductivity ranging from 13.47 to 1009.2 m/day. These values suggested that the aquifer materials are highly permeable, facilitating fluid movement within the aquifer. This research demonstrated the effectiveness of surface geophysics in estimating aquifer hydraulic characteristics, particularly in situations where pumping test data are unavailable. It also highlighted the vulnerability of the aquifer to surface contaminants. The findings are expected to be valuable for the long-term planning of groundwater exploitation projects in the study area.

Integrating shallow head measurements and InSAR data to quantify groundwater-storage change in San Joaquin Valley, California (USA)

Monitoring groundwater storage is essential for sustainable groundwater management. Storage can be quantified by considering the two main components through which storage change is expressed: saturation changes and deformation of aquifer materials. Here, these components were quantified using a selected area in California’s San Joaquin Valley (USA). First, this involved following existing observational approaches: quantifying the component expressed through saturation changes by identifying head measurements from shallow wells and scaling by specific yield. In the San Joaquin Valley, existing approaches to estimate the deformation component are to ignore it or approximate it with a simple linear relation to measured head. However, head and deformation measurements made at extensometers revealed that assuming a linear relationship between deformation and head might provide a poor estimate, particularly during periods in which measured head is rising. Instead, InSAR-derived surface deformation measurements were used to quantify the deformation component of storage changes. This showed that the two components—saturation and deformation—accounted for storage declines of equal magnitude over 2015–2021, suggesting that the deformation component should not be neglected when estimating storage changes in regions with subsidence. Summing the two calculated components gave a new estimate of the total storage change that captured the major trends seen in independent estimates, while better accounting for the deformation component. An additional benefit is that this method accounts for the deformation component in the unconfined aquifer. This method to quantify total storage change can be a practical and effective tool to support groundwater management.

Adsorption of Per- and Polyfluoroalkyl Substances (PFAS) by Aquifer Materials: the Important Role of Dolomite

Adsorption of Per- and Polyfluoroalkyl Substances (PFAS) by Aquifer Materials: the Important Role of Dolomite